Gate cut with integrated etch stop layer

ABSTRACT

A method of forming a power rail to semiconductor devices comprising removing a portion of the gate structure forming a gate cut trench separating a first active region of fin structures from a second active region of fin structures. A conformal etch stop layer is formed in the gate cut trench. A fill material is formed on the conformal etch stop layer filling at least a portion of the gate cut trench. The fill material has a composition that is etched selectively to the conformal etch stop layer. A power rail is formed in the gate cut trench. The conformal etch stop layer obstructs lateral etching during forming the power rail to substantially eliminate power rail to gate structure shorting.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of and claims priority to U.S. patentapplication Ser. No. 17/221,401, filed on Apr. 2, 2021, which is acontinuation of U.S. patent application Ser. No. 16/738,569, filed onJan. 9, 2020, now U.S. Pat. No. 10,998,314, issued May 4, 2021, which isa continuation of U.S. patent application Ser. No. 16/054,394, filed onAug. 3, 2018, now U.S. Pat. No. 10,580,773, issued Mar. 3, 2020, whichis a continuation of U.S. patent application Ser. No. 15/258,513, filedon Sep. 7, 2016, now U.S. Pat. No. 10,083,961, issued Sep. 25, 2018,each of which is incorporated by reference herein in its entirety forall purposes.

BACKGROUND

Technical Field

The methods and structures described herein relate to contact structuresand gate structures used in semiconductor devices, and methods forforming contact structures and gate structures in semiconductor devicesusing subtractive etching.

Description of the Related Art

Modern integrated circuits are made up of literally millions of activedevices such as transistors. Field effect transistors (FETs) are widelyused in the electronics industry for switching, amplification, filteringand other tasks related to both analog and digital electrical signals.Most common among these are metal oxide semiconductor field effecttransistors (MOSFET or MOS), in which a gate structure is energized tocreate an electric field in an underlying channel region of asemiconductor body, by which electrons are allowed to travel through thechannel between a source region and a drain region of the semiconductorbody. Continuing trends in semiconductor device manufacturing include areduction in electrical device feature size (scaling). With increasingscaling, new processing sequences and methods may be required to avoidshorting of adjacent electrical devices.

SUMMARY

In one embodiment, a method of cutting gate structures in a gate cutlast process flow for forming semiconductor devices is provided thatemploys an integrated etch stop layer. In one embodiment, the method maybegin with providing a first active semiconductor region and a secondactive semiconductor region; and forming a gate structure extending fromthe first active region to the second active region. In a followingprocess step, a gate cut removes a portion of the gate structure forminga gate cut trench separating the first active region from the secondactive region. A conformal etch stop layer is formed in the gate cuttrench, wherein a nitride containing fill for the gate cut trench isformed on the conformal etch stop layer. A source power railinterconnect is formed in the gate cut trench, wherein the conformaletch stop layer obstructs lateral etching during forming the sourcepower rail interconnect to substantially eliminate power rail to gatestructure shorting.

In another embodiment, a method of cutting gate structures in a gate cutlast process flow for forming semiconductor devices is provided thatemploys an integrated etch stop layer. In one embodiment, the method maybegin with providing a first active semiconductor region and a secondactive semiconductor region; and forming a sacrificial gate structureextending from the first active region to the second active region. In afollowing process step, a gate cut removes a portion of the sacrificialgate structure forming a gate cut trench separating the first activeregion from the second active region. A conformal etch stop layer isformed in the gate cut trench, wherein a nitride containing fill for thegate cut trench is formed on the conformal etch stop layer. Thesacrificial gate structure is replaced with a functional gate structure.A source power rail interconnect is formed in the gate cut trench,wherein the conformal etch stop layer obstructs lateral etching duringforming the power rail to substantially eliminate opening of theinterlevel dielectric to the sacrificial gate structure.

In another aspect, an electrical device is provided, in which a powerrail is positioned in a gate cut trench positioned between the tip totip distance separating adjacent gate structures, wherein the gate cuttrench is lined with an etch stop layer. In one embodiment, theelectrical device includes a first active region having a first gatestructure; and a second active region having a second gate structure,wherein the first and second gate structures are aligned to one anotherand separated by a gate cut trench. A conformal dielectric layer ispresent on at least sidewall surfaces of the gate cut trench. Adielectric fill in present filling a lower portion of the gate cuttrench. A power rail is present in an upper portion of the gate cuttrench.

BRIEF DESCRIPTION OF DRAWINGS

The following description will provide details for some of the preferredembodiments with reference to the following figures wherein:

FIG. 1 is a top down planar view depicting one embodiment of a gatecontact opening, i.e., CT region, for a semiconductor device that isfilled and pinched off with a dielectric layer.

FIG. 2 is a side cross-sectional view depicting one embodiment of thegate tip to tip critical dimension (CD) for the critical region that isdepicted in FIG. 1 .

FIG. 3A is a top down planar view depicting one embodiment of amisaligned power rail being formed in a gate cut trench.

FIG. 3B is a side cross-sectional view along section line Y-Y(cross-section across the gate cut trench including the power rail) ofFIG. 3A.

FIG. 4A is a top down planar view depicting one embodiment of amisaligned power rail being formed in a gate cut trench, in whichshorting to the substrate and the gate structures is obstructed by anetch stop layer that is positioned in the gate cut trench.

FIG. 4B is a side cross-sectional view along section line Y-Y(cross-section across the gate cut trench including the power rail) ofFIG. 4A, in which the gate cut trench includes two conformal etch stoplayers.

FIG. 4C is a side cross-sectional view along section line Y-Y(cross-section across the gate cut trench including the power rail) ofFIG. 4A, in which the gate cut trench includes a single conformal etchstop layer.

FIG. 5 is a side cross-sectional view (similar to the cross-sectionalong section line X-X of FIG. 1 ) depicting one embodiment of aplurality of gate structures, in which one of the gate structures isetched to provide a gate cut trench.

FIG. 6 is a side cross-sectional view (similar to the cross-sectionalong section line X-X of FIG. 1 ) depicting one embodiment of formingan etch mask including a low temperature oxide (LTO) and an organicplanarization layer (OPL) that exposes one of the gate structuresdepicted in FIG. 5 .

FIG. 7 is a side cross-sectional view (similar to the cross-sectionalong section line X-X of FIG. 1 ) depicting one embodiment of removingthe LTO layer from the structure depicted in FIG. 6 .

FIG. 8 is a side cross-sectional view (similar to the cross-sectionalong section line X-X of FIG. 1 ) depicting one embodiment of etchingthe SiN hard mask and sacrificial liner of the sacrificial gatestructure depicted in FIG. 7 .

FIG. 9 is a side cross-sectional view (similar to the cross-sectionalong section line X-X of FIG. 1 ) depicting one embodiment of removinga sacrificial gate electrode portion of the sacrificial gate structurein a gate cut process flow to define the tip to tip dimension separatingadjacent gate structures on adjacent active field regions of anelectrical device, and forming a etch stop layer in the gate cut trench.

FIG. 10 is a side cross-sectional view (similar to the cross-sectionalong section line X-X of FIG. 1 ) depicting forming a nitridecontaining fill for the gate cut trench on the conformal etch stoplayer.

FIG. 11 is a side cross-sectional view (similar to the cross-sectionalong section line X-X of FIG. 1 ) depicting the active gate afterreplacement gate removal and high-k/metal replacement gate deposition(left) and the cut gate trench filled with the etch stop layer and SiNliner (right). This structure also contains W metal gate recess andself-aligned contact (SAC) SiN Cap deposition and resembles thestructure in FIG. 4C (Y-Y direction) prior to power rail patterning.

FIG. 12 is a side cross-sectional view (similar to the cross-sectionalong section line X-X of FIG. 1 ) depicting another embodiment of aprocess flow that includes two etch stop layers within a gate cuttrench, in which the method includes recessing the nitride containingfill depicted in FIG. 10 .

FIG. 13 is a side cross-sectional view (similar to the cross-sectionalong section line X-X of FIG. 1 ) depicting one embodiment of forming asecond conformal etch stop layer on the recessed surface of the nitridecontaining fill that is depicted in FIG. 12 .

FIG. 14 is a side cross-sectional view (similar to the cross-sectionalong section line X-X of FIG. 1 ) depicting one embodiment of forming asecond fill material atop the second conformal etch stop layer that isdepicted in FIG. 13 .

FIG. 15 is a side cross-sectional view (similar to the cross-sectionalong section line X-X of FIG. 1 ) of the active gate after replacementgate removal and high-k/metal replacement gate deposition (left) and thecut gate trench filled with the etch stop layer and SiN liner (right).This structure also contains W metal gate recess and self-alignedcontact (SAC) SiN Cap deposition and resembles the structure in FIG. 4B(Y-Y direction) prior to power rail patterning.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Detailed embodiments of the claimed structures and methods are disclosedherein; however, it is to be understood that the disclosed embodimentsare merely illustrative of the claimed structures and methods that maybe embodied in various forms. In addition, each of the examples given inconnection with the various embodiments are intended to be illustrative,and not restrictive. Further, the figures are not necessarily to scale,some features may be exaggerated to show details of particularcomponents. Therefore, specific structural and functional detailsdisclosed herein are not to be interpreted as limiting, but merely as arepresentative basis for teaching one skilled in the art to variouslyemploy the methods and structures of the present description. Forpurposes of the description hereinafter, the terms “upper”, “lower”,“right”, “left”, “vertical”, “horizontal”, “top”, “bottom”, andderivatives thereof shall relate to the embodiments of the disclosure,as it is oriented in the drawing figures. The terms “present on” meansthat a first element, such as a first structure, is present on a secondelement, such as a second structure, wherein intervening elements, suchas an interface structure, e.g. interface layer, may be present betweenthe first element and the second element. The term “direct contact”means that a first element, such as a first structure, and a secondelement, such as a second structure, are connected without anyintermediary conducting, insulating or semiconductor layers at theinterface of the two elements.

As used herein, the term “semiconductor device” refers to an intrinsicsemiconductor material that has been doped, that is, into which a dopingagent has been introduced, giving it different electrical propertiesthan the intrinsic semiconductor. Doping involves adding dopant atoms toan intrinsic semiconductor, which changes the electron and hole carrierconcentrations of the intrinsic semiconductor at thermal equilibrium.Dominant carrier concentration in an extrinsic semiconductor determinesthe conductivity type of the semiconductor. As used herein a “fieldeffect transistor” is a transistor in which output current, i.e.,source-drain current, is controlled by the voltage applied to the gate.A field effect transistor has three terminals, i.e., gate structure,source region and drain region. A “gate structure” means a structureused to control output current (i.e., flow of carriers in the channel)of a semiconducting device through electrical or magnetic fields. Asused herein, the term “channel” is the region underlying the gatestructure and between the source and drain of a semiconductor devicethat becomes conductive when the semiconductor device is turned on. Asused herein, the term “source” is a doped region in the semiconductordevice, in which majority carriers are flowing into the channel. As usedherein, the term “drain” means a doped region in semiconductor devicelocated at the end of the channel, in which carriers are flowing out ofthe transistor through the drain.

The etch steps for forming the electrical contacts to the gatestructures of semiconductor devices, such as field effect semiconductordevices (FETs), e.g., metal oxide semiconductor field effect transistors(MOSFETs), and the etch steps for forming power rails for thesemiconductor devices can be an issue leading to device failure insemiconductor devices formed using dummy gate cut last, i.e., CT last,process flow. The term “power rail” denotes an electrical currentcarrying structure that powers the electrical device, i.e., providesvoltage to the semiconductor device. The power rail may be in electricalcommunication with at least one of the source region or the drain regionof the semiconductor device.

In dummy gate cut last (CT last) process flow, the etch process forcutting the dummy gate structure, i.e., sacrificial gate structure, isafter the formation of the source and drain epitaxial material; afterthe formation of an interlevel dielectric over the source and drainregions; and after a planarization process that is applied to theinterlevel dielectric so that the upper surface of the interleveldielectric is coplanar with the upper surface of the dummy gatestructure. It has been determined that in some process flows, thenitride liners, e.g., silicon nitride liners, that are present in thegate cut trench can be etched by the process sequence for forming thepower rail, which can cause shorting between the power rail and the gatestructures due to lateral etching that typically occurs while formingthe openings for the power rail in the gate cut trench. A short CBopening, i.e., a gate contact opening having a short height, should landon the top of the active gate. The long CB power rail, i.e., the sourceinterconnection with runs through the cut gate (metal), sits within thegate cut trench for the dummy gate, i.e., CT region (trench separatingportions of the gate structures on separate active regions), and cancause shorting between the power rail, and the replacement metal gatestructure. The replacement metal gate structure, i.e., PC, is typicallya dummy gate structure (also referred to as a sacrificial gatestructure), such as one composed of silicon, i.e., dummy silicon, thateventually is replaced with an active gate during the replacement metalgate module. In other examples, the etch process for forming theelectrical contact to the gate, i.e., CB contact, includes an over-etchinto the substrate, which can lead to leakage between the substrate andthe power rail contact.

In some embodiments, the methods and structures disclosed herein preventetching of the electrical contact (CB) power rail opening from etchinginto the underlying substrate. In some embodiments, the methods andstructures disclosed herein prevent electrical contact (CB) power railand critical dimension (CD) blow-up during reactive ion etching (ME) ofsilicon nitride liners that are present in the dummy gate trench, i.e.,(CT) trench. In some embodiments, the methods and structures disclosedherein provide an etch stop layer within the dummy gate trench, i.e.,(CT) trench, in which the etch stop layer helps to avoid etching of theelectrical contact (CB) opening into the substrate, and the etch stoplayer helps to prevent electrical contact (CB) and critical dimension(CD) blow-up. The methods and structures disclosed herein may use a PC“cut last” method to define active gate regions post spacer/EPI module.This process can be demonstrated in Poly Open chemical mechanicalplanarization (CMP) (POC) or replacement metal gate (RMG) modules. Thisprocess improves PC or gate “tip-to-tip” dimension or the gate cut width(distance between cut gate lines) (PC T2T) window for scaling.

In some embodiments, the methods disclosed herein can prevent two issuesin the middle of the line (MOL) module. In some examples, the methodsand structures disclosed herein can prevent CB CD blow-up, i.e., anincreased in the power rail contact (CB) critical dimension (CD), duringCB RIE, i.e., reactive ion etch for forming the electrical contact tothe gate structure (CB). The CB power rail, i.e., source/drain contactthat runs through the cut gate (metal), which runs along the CT region,i.e., gate trench opening, that is filled with SiN can be laterallyetched during processing for forming the CB gate contact to the gatemetal. The selective SiN etch integrated into the CB contact RIE processis intended to etch through the SiN self-aligned contact cap (SAC Cap).This part of the etch process exposes the active gate metal for contactformation, but also laterally blows-up the CB power rail contact CDwithin the CT trench region due to the SiN CT liner fill. In some otherexamples, the methods and structures disclosed herein can prevent powerrail over-etch during CB RIE, i.e., the reactive ion etch process forforming the gate contact (CB) to the gate metal and for forming thepower rail interconnect contact to the source regions of devices fromover-etching into the substrate, which can lead to parasitic leakage andpotentially substrate shorting.

In some embodiments, the methods and structures provide a number ofadvantages in the Replacement Metal Gate (RMG) and Poly Open Chemicalmechanical planarization (CMP) (POC) process modules. For example, thegate cut-last methods and structures may prevent source to drainepitaxial shorting around a cut end of dummy gate structure (PC), i.e.,the end line of the dummy gate structure (PC). In one example, themethods and structures may preserve sidewall spacers by eliminating therequirement to cut the dummy gates prior to source/drain EPI formation.Dummy gate cut prior to spacer deposition results in an exposed corneredge which is more vulnerable to pull-down and exposure of a-Si duringspacer RIE etch-back. Gate cut-last after the spacer and EPI formationreduces the threat of exposing the amorphous silicon (α-Si) of the dummygate structure, and avoids subsequent parasitic epitaxial nodule growth.This parasitic nodule growth can result in incomplete poly open contact(POC) poly pull middle of the line (MOL) contact opens, and localvariations in uniformity that degrades the replacement metal gate (RMG)module. In further examples, the methods and structures disclosed hereinprovide for improved gate tip-to-tip scaling in static random accessmemory (SRAM) logic circuits. In some other examples, the methods andstructures disclosed herein minimize the incidence of source/drain togate contact shorting in devices using a shared local interconnect. Themethod and structures for employing gate cuts with integrated etch stoplayers, are now described in more detail with reference to FIGS. 1-15 .

FIG. 1 is a top down view depicting one embodiment of a gate cut trench5, i.e., CT region, that is filled and pinched off with a dielectriclayer, e.g., silicon nitride layer (SiN). The CB power rail, i.e., thelocal interconnect signal line which connects transistor source contactregions that runs through the cut gates on STI (shallow trenchisolation), is identified in FIG. 1 by reference number 10. Source/drainregions are identified by reference number 15. The source contactregions that are connected to the CB power rail are identified byreference number 15′. The intersection of the source regions 15′, the CBpower rail 10 and the CT region 5 is a critical region, as labeled inFIG. 1 .

FIG. 2 is a side cross sectional view of the critical region (Y-Y)depicted in FIG. 1 . The gate tip to tip critical dimension (CD) isidentified by CD1. The gate cut trench 5 is present within the criticaldimension (CD) and is typically filled with a nitride fill material 30,such as silicon nitride. The nitride fill material 30 within the gatecut trench 5 separates a first gate structure 25 a that is present overa first active region 30 a from a second gate structure 25 b that ispresent over a second active region 30 b. It has been determined thatthe etch step (which includes forming the etch mask identified byreference number 35 using lithography and pattern transfer) includes anetch chemistry that is selected to etch the nitride of the SAC Cap (notlabeled) on active gates and to land a contact on the gate metal, butthe etch process can cause lateral blow-up, i.e., lateral etching to thesidewalls of the gate structures 25 a, 25 b, within the SiN filled CTtrench which can short the power rail to the adjacent active gatestructures (identified by reference number 24 a). This can be worse withlithography containing poor overlay, i.e., misalignment of the etch mask35. Additionally, the over etching can cause a short to the substrate(identified by reference number 24 b).

FIGS. 3A and 3B illustrate one example of a misaligned power rail 10being formed in a gate cut trench 5. FIGS. 3A and 3B illustrate a gatecut trench 5 that is only filled with a nitride fill material 30, suchas silicon nitride. FIGS. 3A and 3B illustrate that the misaligned powerrail 10 shorting to the first gate structures 25 a overlying the firstactive region due to the misalignment of the power rail 10, and/or overetching in a lateral direction towards the first gate structures 25 a.More specifically, the metal, e.g., contact metal liner and tungsten(W), of the power rail 10 directly contacts the gate metal, e.g.,tungsten (W) and Work Function Metal (WFM). This is illustrated by theinterface identified by reference number 26. FIGS. 3A and 3B furtherillustrate that over etching in the vertical direction can result in themetal, e.g., tungsten (W), of the power rail 10 contacting asemiconductor substrate 1, which may also short the device. This isillustrated by the interface identified by reference number 127.

FIGS. 4A-4C depict a misaligned power rail 10 being formed in a gate cuttrench 5, in which shorting to the substrate and the gate structures 25a, 25 b is obstructed by an etch stop layer 40 a, 40 b that ispositioned in the gate cut trench 5. FIGS. 4A-4C illustrate oneembodiment of an electrical device that includes a first active region30 a having a first gate structure 25 a; and a second active region 30 bhaving a second gate structure 25 b. The first and second active regions30 a, 30 b are the portions of the electrical device including at leasta channel portion of a semiconductor device, such as a field effecttransistor (FET). In some embodiments, the first and second activeregions 30 a, 30 b may include at least one fin structure, e.g., whenthe FETs being formed are fin-type field effect transistors (FETs). Asused herein, a “fin structure” refers to a semiconductor material, whichis employed as the body of a semiconductor device, in which the gatestructure is positioned around the fin structure such that charge flowsdown the channel on the two sidewalls of the fin structure andoptionally along the top surface of the fin structure. The portions ofthe fin structure adjacent on the opposing sides of the channel portionare the source and drain region portions of the fin structure. Thesource and drain regions of the semiconductor devices may be doped to ann-type or p-type conductivity. The fin structures may be composed of atype IV semiconductor, such as silicon (Si), germanium (Ge) or acombination thereof, e.g., silicon germanium (SiGe), or the finstructures may be composed of a type III-V semiconductor, such asgallium arsenic (GaAs).

Referring to FIGS. 4A-4C, the first and second gate structures 25 a, 25b are aligned to one another and separated by a gate cut trench 5. Byaligned it is meant that the centerline of the first gate structure 25 a(that is perpendicular to the channel length) is aligned to thecenterline of the second gate structure 25 b. As will be furtherdescribed below, a gate cut etch is applied to the portion of ansacrificial gate structure separating the portion of the sacrificialgate structure, i.e., first portion, that is present on the first activeregion 30 a from the portion of the sacrificial gate structure, i.e.,second portion, that is present on the second active region 30 b. Thefirst portion of the sacrificial gate structure provides the first gatestructure 25 a, and the second portion of the sacrificial gate structureprovides the second gate structure 25 b.

Each of the first and second gate structures 25 a, 25 b may include atleast one gate dielectric 27 and at least one gate conductor 26. In oneembodiment, the gate dielectric 27 may be composed of silicon oxide, ora high-k dielectric material, such as hafnium oxide (HfO₂). The gateconductor 26 may be composed of a conductive material, such as a metal,such as tungsten (W), or a doped semiconductor, e.g., n-type dopedpolysilicon. In some embodiments, the first and second gate structures25 a, 25 b may further include an n-type or p-type work function metal(WFM) 22, e.g., titanium nitride. As will be described in further detailbelow the gate structures 25 a, 25 b may be formed using gate last,i.e., replacement gate processing, e.g., replacement metal gate (RMG)processing. In some embodiments, each of the first and second gatestructures 25 a, 25 b may include a dielectric gate cap 28. Thedielectric gate cap 28 may include a nitride material, such as siliconnitride.

Still referring to FIGS. 4A-4C, gate sidewall spacers 29 may be presenton the sidewalls of the gate structure 25 a, 25 b. The gate sidewallspacers 29 may be composed of a dielectric material, such as an oxide,nitride or oxynitride material. In some embodiments, the gate sidewallspacers 29 may be composed of silicon nitride. The gate sidewall spacers29 may be formed using a deposition process, such as chemical vapordeposition (CVD), followed by an etch back process. This process iscompleted after replacement gate formation and during the source/drainepitaxy modules.

The first gate structure 25 a is separated from the second gatestructure 25 b by a gate cut trench 5, which can dictate the tip to tip(T2T) dimension that is separating the gate structures, which can be acritical dimension CD1. In some embodiments, the critical dimension CD1may range from 20 nm to >100 nm. This range is suitable for staticrandom access memory (SRAM) devices to large field effect transistor(FET) macros. In some other embodiments, the critical dimension CD1 mayrange from 18 nm to 25 nm. This range is suitable for static randomaccess (SRAM) devices for more aggressively scaled devices. The gate cuttrench 5 may be at least partially filled with a dielectric material,such as silicon nitride. As will be further described below, the CBpower rail 10 for the electrical device may be positioned within thegate cut trench 5.

FIGS. 4A-4C illustrate a conformal dielectric layer 40 a, 40 b (alsoreferred to as conformal etch stop layer 40 a, 40 b) on at leastsidewall surfaces of the gate cut trench 5. The term “conformal” denotesa layer having a thickness that does not deviate from greater than orless than 30% of an average value for the thickness of the layer. Thecomposition for the conformal dielectric layer 40 a, 40 b is selected toprovide that the etch process steps for forming the opening in the gatecut trench 5 does not increase the width or depth of the gate cut trench5 in a manner that would expose a portion of the gate structures 25 a,25 b or expose the underlying substrate 1. In some embodiments, theconformal etch stop layer 40 a, 40 b may be composed of hafnium oxide(HfO₂). In other embodiments, the conformal etch stop layer 40 a, 40 bmay be composed of cerium oxide (CeO₂), lanthanum oxide (La₂O₃), yttriumoxide (Y₂O₃), gadolinium oxide (Gd₂O₃), europium oxide (Eu₂O₃), terbiumoxide (Tb₂O₃) or combinations thereof. It is noted that the abovecompositions are provided for illustrative purposes only, and are notintended to limit the methods and structures described herein. Forexample, the conformal etch stop layer 40 a, 40 b may also be composedof other rare earth containing metal oxides. In some embodiments, therare earth metal of the conformal etch stop layer 40 a, 40 b is selectedfrom the group consisting of Lanthanum (La), Cerium (Ce), Praseodymium(Pr), Neodymium (Nd), Promethium (Pm), Samarium (Sm), Europium (Eu),Gadolinium (Gd), Terbium (Tb), Dysprosium (Dy), Holmium (Ho), Erbium(Er), Thulium (Tm), Ytterbium (Yb), Luthium (Lu), and a combinationthereof. Exemplary are earth oxides may include cerium oxide (CeO₂),lanthanum oxide (La₂O₃), yttrium oxide (Y₂O₃), gadolinium oxide (Gd₂O₃),europium oxide (Eu₂O₃), and terbium oxide (Tb₂O₃)). It is noted that insome embodiments any composition may be employed so long as it isselective to silicon nitride.

In some embodiments, the conformal dielectric layer 40 a, 40 b functionsas an etch stop layer, in which the conformal dielectric layer 40 a, 40b obstructs the power rail from shorting to the first and second gatestructure. In some embodiments, the conformal dielectric layer 40 a, 40b may have a thickness that ranges from 1 nm to 100 nm. In otherembodiments, the conformal dielectric layer 40 a, 40 b may have athickness ranging from 2 nm to 75 nm. In yet other embodiments, theconformal dielectric layer 40 a, 40 b may have a thickness ranging from5 nm to 25 nm. It is noted that the above examples are provided forillustrative purposes only, and are not intended to limit the methodsand structures described herein.

Referring to FIGS. 4A and 4C, in some embodiments a first conformaldielectric layer 40 a is present on the base of the gate cut trench 5atop the substrate 1, and at least the sidewalls of the gate cut trench5 in a lower portion of the gate cut trench 5. In other embodiments, thefirst conformal layer 40 a may extend along a height of the entirety ofthe sidewall of the gate cut trench 5. Referring to FIGS. 4A and 4B, inother embodiments, the conformal dielectric layer 40 a, 40 b may includemultiple layers. For example, a first conformal dielectric layer 40 amay be present on the base of the gate cut trench 5 and on the sidewallsof the gate cut trench 5, in which a gate cut trench fill material 45 ispresent on the first conformal dielectric layer 40 a. In thisembodiment, a second conformal dielectric layer 40 b may be present inthe upper portion of the gate cut trench 5, in which the secondconformal dielectric layer 40 b is present on the gate cut trench fillmaterial 45 and is present on the sidewalls of the upper portion of thegate cut trench 5. The second conformal dielectric layer 40 b canobstruct the etch process steps for forming the opening, i.e., CBopening, for the CB power rail from etching too deeply into the gate cuttrench 5, i.e., obstructs the etch process steps for forming the CBopening from contacting the substrate. For example, the second conformaldielectric layer 40 b can protect the gate cut trench fill material 45from being etched. It is noted that the first conformal dielectric layer40 a, and the second conformal dielectric layer 40 b may be composed ofthe same composition material, or that the first conformal dielectriclayer 40 a and he second conformal dielectric layer 40 b may have adifferent composition material. Referring to FIGS. 4A-4C, a power rail10 is present in an upper portion of the gate cut trench 5. The powerrail 10 may be composed of an electrically conductive material. Forexample, the power rail 10 may be composed of tungsten (W). In otherembodiments, the power rail 10 may be composed of a metal that isselected from cobalt (Co), ruthenium (Ru), titanium (Ti), aluminum (Al),copper (Cu) and combinations thereof. As depicted in FIGS. 4A and 4B,the power rail 10 may be in direct contact with the conformal dielectriclayer, e.g., second conformal dielectric layer 40 b. The conformaldielectric layer 40 a, 40 b may separate the power rail 10 from the gateconductors 26 of the first and second gate structures 25 a, 25 b;therefore obstructing the power rail 10 from shorting to the first andsecond gate structures 25 a, 25 b.

The structures depicted in FIGS. 4A-4C illustrate some embodiments ofthe structures provided herein. Some embodiments of methods for formingstructures, as depicted in FIGS. 4A-4C, as well as similar power railincluding structures, are now described in greater detail with referenceto FIGS. 5-15 . FIGS. 5-15 represent the process flow of the gate cutlast method with depositing conformal etch stop layers in the gate cuttrench region. These figures describe the process flow to form an activeand cut gate along the X-X cross-section direction from FIG. 1 and donot contain the CB power rail as shown in FIG. 1 Y-Y, FIG. 2 , FIG.3A-3B or FIG. 4A-4C.

The process flow depicted in FIGS. 5-11 illustrates one embodiment offorming a structure including the power rail depicted in FIGS. 4A and4C. FIG. 5 depicts a plurality of sacrificial gate structures 25′, inwhich one of the gate structures 25′ is etched to provide arepresentation gate cut trench 5. The sacrificial gate structures 25′are formed atop active regions of the electrical device, at which achannel region of a semiconductor device is present. As described above,the active regions may include fin structures, in which thesemiconductor devices being formed are fin type field effect transistors(FinFETs). The sacrificial gate structures 25′ are composed of amaterial that may be removed selectively to the underlying activeregion, in which the geometry of the sacrificial gate structures 25′dictates the later formed functional gate structures, in which thesacrificial gate structures 25′ may be replaced using a replacementmetal gate (RMG) process flow. In some embodiments, the sacrificial gatestructures 25′ may be composed of a semiconductor material, such assilicon (Si), e.g., amorphous silicon or polysilicon. In someembodiments, a sacrificial gate cap or hard mask 28′, 28″ may be presentatop the sacrificial gate conductor. In some embodiments, thesacrificial gate hard mask may include an oxide layer 28″, e.g., siliconoxide (SiO₂) layer, present atop the gate conductor portion of thesacrificial gate structure 25′, in which a nitride layer 28′, e.g.,silicon nitride hard mask layer, is present on the oxide layer 28″. Insome embodiments, an alternative gate hard mask material can be usedwhich offers the required etch selectivity for processing.

Following the formation of the sacrificial gate structures 25, sourceand drain regions may be formed in each of the active regions. In someembodiments, a sidewall spacer dielectric film 29 is deposited over allstructures and etched back to expose the source/drain epitaxy surface.The source and drain regions may be formed by ion implantation or byforming an in-situ doped epitaxial semiconductor material. For example,when the active regions include fin structures, the source and drainregions may be formed by epitaxially forming in situ doped semiconductormaterial on the portions of the fin structures that are on opposingsides of the channel region of the fin structures.

Following formation of the source and drain regions, an interleveldielectric layer 31 is formed between and over the sacrificial gatestructures 25′, the active regions, and the source and drain regions.The interlevel dielectric layer 31 may be formed using a depositionmethod, such as chemical vapor deposition (CVD), e.g., plasma enhancedchemical vapor deposition (PECVD), deposition from chemical solution, orspin on deposition. Following deposition, the interlevel dielectriclayer 31 is planarized, e.g., planarized by chemical mechanicalplanarization (CMP), so that the upper surface of the interleveldielectric layer 31 is coplanar with the upper surface of the hard mask28′ in the sacrificial gate structures 25′.

FIG. 5 also depicts one embodiment of forming a blanket dielectric layer46 atop the planarized upper surface of the interlevel dielectric layer31 and the sacrificial gate cap 28′, 28″. The blanked dielectric layer46 may be composed of a nitride, such as silicon nitride. The blanketdielectric layer 46 may be deposited using chemical vapor deposition,e.g., plasma enhanced chemical vapor deposition, atomic layerdeposition, chemical solution deposition or spin on deposition.

FIG. 6 depicting one embodiment of forming an etch mask 50 including alow temperature oxide (LTO) 51 and an organic planarization layer (OPL)52 that exposes one of the sacrificial gate structures 25′ depicted inFIG. 5 . The etch mask 50 that is depicted in FIG. 6 may be employed forthe gate cut etch that determines the tip to tip (T2T) criticaldimension (CD) that separates the gate structure present on the firstactive region from the gate structure that is present on the secondactive region. The gate cut etch formed the gate cut trench 10.

The organic planarization layer 52 can include a polyacrylate resin,epoxy resin, phenol resin, polyamide resin, polyimide resin, unsaturatedpolyester resin, polyphenylenether resin, polyphenylenesulfide resin, orbenzocyclobutene (BCB). The organic planarization layer 52 can bedeposited using chemical vapor deposition and/or spin on deposition. Thelow temperature oxide 51 is typically composed of silicon oxide (SiO₂),which can be formed using chemical vapor deposition (CVD).

The LTO layer 51 and the OPL 52 may be patterned and etched to providean etch mask for gate cut etch that forms the gate cut trench 10. TheLTO 51 and the OPL layer 52 may be patterned using photolithography andetch processes. Specifically, and in one example, an etch mask patternis produced by applying a photoresist to the surface to be etched,exposing the photoresist to a pattern of radiation, and then developingthe pattern into the photoresist utilizing a resist developer. Once thepatterning of the photoresist is completed, the sections of the LTOlayer 51 and the OPL layer 52 covered by the photoresist are protected,while the exposed regions are removed using a selective etching process.The term “selective” denotes that a first material may be etched at afaster rate to a second material. For example, the selective etch ratemay remove a first material at a rate greater than 20:1, e.g., greaterthan 100:1, in comparison to a second material. The etch process may bereactive ion etch (RIE), which can be selective to blanket dielectriclayer 46.

FIG. 7 depicts one embodiment of removing the LTO layer 51 from thestructure depicted in FIG. 6 . The LTO layer 51 may be removed by anetch that is selective to the OPL layer 52. The etch process forremoving the LTO layer 51 may also selective to the exposed portion ofthe blanket dielectric layer 45. The etch process for removing the LTOlayer 51 may be an anisotropic etch or an isotropic etch. In someembodiments, the LTO layer 51 may be removed using reactive ion etch(ME) and/or a wet chemical etch. In some embodiments, the LTO layer 51and OPL layer 52 may be omitted, as any patterning mechanism includingthose not requiring the LTO layer 21 and the OPL layer 52 may be used atthis point of the process flow.

FIG. 8 depicts one embodiment of removing the exposed portion of theblanket dielectric layer 46, and selectively etching the replacementgate SiN hard mask 28′ on top of 25′ as seen in FIG. 7 . The patternedreplacement gate SiN hard mask 28′is the portion of the sacrificial gatestructure 25′ that will be etched to provide the gate cut, i.e., thegate cut trench 5 that provides the tip to tip (T2T) dimensionseparating adjacent gate structures. The etch process for recessing thesacrificial gate hard mask 28′ may also recess the exposed gate sidewallspacers 29. The etch process for removing the exposed portion of theblanket dielectric layer 46, selectively etching the sacrificial gatehard mask 28′, and recessing the exposed gate sidewall spacers 29 may bean anisotropic etch, such as reactive ion etch (ME), gas plasma etchingor laser milling/laser etching. This dry etching technique is desired tomaintain gate cut tip-to-tip critical dimensions without lateralundercut of SiN beneath the OPL layer 52. In other embodiments, the etchprocess for removing the exposed portion of the blanket dielectric layer46, selectively etching the sacrificial gate hard mask 28′, andrecessing the exposed gate sidewall spacers 29 may be an isotropic etch,such as a wet chemical etch. In some embodiments, the etch process forremoving the exposed portion of the blanket dielectric layer 46,selectively etching the sacrificial gate hard mask, and recessing theexposed gate sidewall spacers 29 may be a combination of anisotropicetching, e.g., reactive ion etching (RIE) and isotropic etching, e.g.,wet chemical etching.

In some embodiments, the remaining portion of the organic planarizationlayer (OPL) 52 may then be removed using a selective etch. FIG. 9depicts one embodiment of selectively etching the remaining sacrificialgate electrode portion of the sacrificial gate structure 25′ in a gatecut process flow to define the tip to tip dimension separating adjacentgate structures on adjacent active field regions of an electricaldevice. The etch process for removing the exposed sacrificial gatestructure 25′ may be selective to the remaining portion of the gatesidewall spacers 29 and sacrificial SiN liner 46 that are exposed by themask composed of the patterned organic planarization layer 52. Removingthe remaining portion of the sacrificial gate structure 25′ produces thegate cut trench 5.

FIG. 9 depicts the selective etching of the sacrificial gate structure25′ to form the gate cut and the subsequent selective etch stop layer 40a within the gate cut trench 5. The sacrificial gate structure 25′ isremoved by an anisotropic etching process to maintain required gatetip-to-tip dimensions. In one embodiment, the sacrificial gate structure25′ is removed by reactive ion etch (ME).

FIG. 9 further depicts one embodiment of forming a first conformaldielectric layer 40 a, i.e., first etch stop layer 40 a, within the gatetrench opening 5. The first conformal dielectric layer 40 a is depositedusing a conformal deposition process on the sidewalls and base of thegate trench opening 5. The first conformal dielectric layer 40 a isformed on the gate sidewall spacers 29 that are present within the gatetrench opening 5. The first etch stop layer 40 a may be deposited usinga conformal deposition technique to fill high aspect ratio trenches,such as Atomic Layer Deposition (ALD). In some embodiments, chemicalvapor deposition (CVD) may be suitable method for etch-stop layerdeposition. The composition of the first conformal dielectric layer 40 amay be composed of hafnium oxide (HfO₂). The composition of the firstconformal dielectric layer 40 a is selected to function as an etch stoplayer that obstructs the sidewalls of the gate cut trench 5 from beinglaterally etched by etch processes for forming a power rail 10 withinthe gate cut trench 5. The composition of the first conformal dielectriclayer 40 a also functions as an etch stop to control over etch so thatthe substrate 1 that is underlying the gate cut trench 5 is not etchedby the etch process for forming the power rail 10.

FIG. 10 depicts forming a nitride containing fill 45 within the gate cuttrench 10 on the first conformal dielectric layer 40 a, i.e., firstconformal etch stop layer 40 a. In some embodiments, the nitridecontaining fill 45 may be composed of silicon nitride. The nitridecontaining fill 45 should be deposited using a conformal depositionprocess to fill high aspect ratio trenches, or a bottom-up depositiontechnique to ensure that there are no voids formed by dielectricpinch-off at the top of the trench opening. In some embodiments, thenitride fill 45 is deposited using atomic layer deposition (ALD) processfor conformal sidewall coverage which prevents pinch-off. In someembodiments, a cyclic deposition and etch-back deposition sequenceprocess may be used to perform a bottom-up nitride fill within the gatecut trench. This film may be deposited using a chemical vapor deposition(CVD) process that may include Atmospheric Pressure CVD (APCVD), LowPressure CVD (LPCVD), Plasma Enhanced CVD (PECVD), Metal-Organic CVD(MOCVD) and combinations thereof. In some embodiments, the nitridecontaining fill 45 may be deposited to fill the entirety of the gate cuttrench 5. In some embodiments, a portion of the nitride containing fill45 may overfill the gate cut trench 5 extending onto the upper surfaceof the interlevel dielectric 31 and the remaining portion of the blanketdeposited nitride layer 46.

FIG. 11 is a side cross-sectional view having the orientation alongsection line X-X (as illustrated in FIG. 1 ) depicting the finalstructure of the active gate and cut gate prior to middle of line (MOL)contact patterning and etching of the power rail interconnect. Thestructure in FIG. 10 is planarized using chemical mechanicalplanarization (CMP), which removes the portion of the nitride containingfill 45 that extends outside the gate cut trench 5. The planarizationprocess may also remove a remaining portion of the blanket nitride layer46 to expose the gate hard mask 28′ cap above the sacrificialreplacement gate structure 25′. The gate hard mask 28′ is thenselectively removed using an anisotropic reactive ion plasma etch (RIE)that preserves the interlevel dielectric 31 height. After the gate hardmask etching the replacement gate in the active regions 25 a, 25 b isselectively removed using an isotropic etching process which isselective to both interlevel dielectric 31, sidewall spacers 29 anddielectric gate cut fill liners 45, 40 a and 40 b. This selectiveremoval of the replacement Silicon uses a wet chemistry which can beammonium hydroxide (NH₄OH) or Tetraethylammonium Hydroxide (TEAH).Selective dry etching based techniques can also be used to etch thedummy gate Silicon to expose the active fin channels within the gatestructures.

A functional gate structure 25 a is formed in the space that is providedby removing the sacrificial gate structure 25′. After the dummy gatesilicon is selectively removed from the PC in the active areas to exposethe fin channels, the dummy gate oxide on the fins is removed using adry or wet etch. The fin surface is then pre-cleaned using a dilute HF(DHF) etch and high-k oxide is deposited on the fins to serve as thegate dielectric.

In some embodiments, the functional gate structure 25 a is formed indirect contact with a channel region portion of the fin structures inthe active region of the device. The functional gate structure 25 atypically includes at least one gate dielectric layer 27 and at leastone gate conductor layer 26. The at least one gate dielectric layer 27is typically positioned directly on at least the channel portion of thefin structures in the active regions of the substrate 1. The at leastone gate dielectric layer 27 may be formed by a thermal growth process,such as, e.g., oxidation, nitridation or oxynitridation. The at leastone gate dielectric layer 27 may also be formed by a deposition process,such as, e.g., CVD, plasma-assisted CVD, MOCVD, ALD, evaporation,reactive sputtering, chemical solution deposition and other likedeposition processes. The at least one gate dielectric layer 27 may alsobe formed utilizing any combination of the above processes.

The at least one gate dielectric layer 27 may be comprised of aninsulating material having a dielectric constant of about 4.0 orgreater. In another embodiment, the at least one gate dielectric layer27 is comprised of an insulating material having a dielectric constantgreater than 7.0. The dielectric constants mentioned herein are relativeto a vacuum. In one embodiment, the at least one gate dielectric layer27 employed in the present description includes, but is not limited to,an oxide, nitride, oxynitride and/or silicates including metalsilicates, aluminates, titanates and nitrides. In one example, when theat least one gate dielectric layer 27 is comprised of an oxide, theoxide may be selected from the group including, but not limited to,SiO2, HfO2, ZrO2, Al₂O₃, TiO₂, La₂O₃, SrTiO₃, LaAlO₃, Y₂O₃ and mixturethereof. The physical thickness of the at least one gate dielectriclayer 27 may vary, but typically, the at least one gate dielectric layer27 has a thickness from 1 nm to 10 nm. In another embodiment, the atleast one gate dielectric layer has a thickness from 1 nm to 3 nm.

After forming the material layer for the at least one gate dielectriclayer 27, a layer of a conductive material which forms the at least onegate conductor 26 of functional gate structure 25 a is formed on the atleast one gate dielectric 27 utilizing a deposition process, such asphysical vapor deposition (PVD), CVD or evaporation.

In some embodiments, the conductive film may be composed of a workfunction metal (WFM) to set the required threshold voltage for both NFETand PFET. This WFM may be different between NFET and PFET and composedof several stacked layers of conductive liners. The conductive materialmay comprise polysilicon, SiGe, a silicide, a metal or ametal-silicon-nitride such as Ta-Si-N. Examples of metals that can beused as the conductive material include, but are not limited to, Al, W,Cu, and Ti, TiN, TiC or other like conductive metals. The layer ofconductive material may be doped or undoped. If doped, an in-situ dopingdeposition process may be employed. Alternatively, a doped conductivematerial can be formed by deposition, ion implantation and annealing.

The bulk gate metal, e.g. W, is then planarized using a chemicalmechanical planarization (CMP) process and subsequently recessed belowthe top of the spacers 29 and interlevel dielectric 31 using a selectivedry etch process. A self-aligned contact cap layer (such as SiN) isdeposited in the recessed cavity and is then planarized to form themiddle of line SAC Cap layer on active gates. This is the final activegate structure shown in FIG. 11 (left) and the neighboring cut gatetrench is filled with SiN and the selective stop layers.

Forming the power rail 10 may begin with forming a power rail opening inthe gate cut trench 5. The power rail opening may be formed into thenitride containing fill 45. The power rail openings may be formed usingphotolithography and etch processes. Specifically, and in one example, aetch mask pattern is produced by depositing a patterning stack andapplying a photoresist to the surface to be etched, exposing thephotoresist to a pattern of radiation, and then developing the patterninto the photoresist utilizing a resist developer. Once the patterningof the photoresist is completed, the sections of the structure coveredby the photoresist are protected, while the exposed regions are removedusing a selective etching process that removes the unprotected regionsto form power rail openings in the gate cut trench 5. The etch processfor forming the power rail openings may include reactive ion etch (RIE),which is selective to the first conformal dielectric layer 40 a, whichprovides a first conformal etch stop layer 40 a. The etch stop obstructslateral etching that would increase the tip to tip dimension of the gatecut trench 5, as well as obstructing vertical etching that could cutthrough the base of the gate cut trench 5 into the underlying substrate1

In one example, the first step of the CB power rail etch includes a SiO₂etch component to etch down through an oxide patterning layer, which isinitially deposited on top of the self-aligned contact SiN Cap. In priormethods, this process etches through the “etch stop” portion on thesidewalls of the cut PC region and form a trench within the CT region,i.e., gate cut trench 5, as depicted in FIGS. 3A and 3B. In someembodiments of the methods and structures described herein, as depictedin FIGS. 4A-4C, the second step to the CB power rail etch is a SiN etchof the self-aligned cap (SAC), also referred to as gate dielectric cap28, to expose the gate structure, i.e., gate conductor portion of thegate structure. In this example, the etch process, e.g., reactive ionetch (ME) for forming the opening to the gate structure for the gatecontact, i.e., CB gate contact, and the opening within the gate cuttrench 5 for the power rail 10, i.e., CB power rail, can be the sameetch process, i.e., in the same step.

The conformal dielectric layer 40 a, which can be composed of HfO₂, canovercome this problem, wherein the conformal dielectric layer 40 aregions of the gate cut trench 5 fill, i.e., CT fill, obstruct shortingof the active gate (CD blow-up/overlay problems) or shorting through thesubstrate by etching downward (potentially through a seam/void in theSiN CT liner fill). The bottom etch stop layer 40 a prevents this etchinto the substrate 1 and the sidewall (on the gate tip-to-tip sections)prevents lateral CB power rail etch into the gate 25.

Following formation of the power rail openings, the power rail openingsmay be filled with an electrically conductive material to provide thepower rail 10. The electrically conductive material of the power rail 10may be a metal, such as aluminum, copper, tungsten, titanium, tantalum,platinum, gold, silver or a combination thereof. In some embodiments,the electrically conductive material of the power rail 10 may bedeposited using physical vapor deposition (PVD), chemical vapordeposition (CVD) or atomic layer deposition (ALD) methods. In oneexample, in which the metal layer of nickel (Ni) and platinum (Pt) isdeposited by physical vapor deposition (PVD) method, the depositionprocess may include sputtering. Examples of sputtering apparatus thatmay be suitable for depositing the electrically conductive material forthe power rail 10 include DC diode type systems, radio frequency (RF)sputtering, magnetron sputtering, and ionized metal plasma (IMP)sputtering. In another example, the metal layer including nickel (Ni)and platinum (Pt) within the via opening 15 using plating processes,such as electroplating or electroless plating. In the embodiments, inwhich electrically conducive material may be deposited into the powerrail openings using chemical vapor deposition (CVD), in which thechemical vapor deposition (CVD) process may be selected from the groupconsisting of Atmospheric Pressure CVD (APCVD), Low Pressure CVD (LPCVD)and Plasma Enhanced CVD (PECVD), Metal-Organic CVD (MOCVD) andcombinations thereof may also be employed. It is noted that theaforementioned examples of deposition processes are provided forillustrative purposes only, and are not intended to limit the methodsand structures described herein, as other deposition processes may beequally applicable, so long as enough material may be deposited withinthe power rail openings to provide the power rail 10.

FIGS. 5-11 depict one embodiment of a method of forming a power rail 10in a gate cut trench 5 including only one conformal etch stop layer,i.e., a first conformal dielectric layer 40 a, that obstructs lateraletching and over-etching during the process sequence for forming thepower rail, as depicted in FIGS. 4A and 4C.

FIGS. 12-15 depict another embodiment, in which the method for formingthe power rail 10 in a gate cut trench 5 including only two conformaletch stop layers, a first conformal dielectric layer 40 a and a secondconformal dielectric layer 40 b, as depicted in FIGS. 4A and 4B.Referring to FIG. 12 , in one embodiment of the method that includes twoetch stop layers, e.g., first conformal dielectric layer 40 a and asecond conformal dielectric layer 40 b, may begin with recessing thenitride containing fill 45 that is depicted in FIG. 10 . The nitridecontaining fill 45, which for this embodiment may be referred to as afirst nitride containing fill 45, may be recessed using an etch process,such as reactive ion etch (RIE). The depth at which the first nitridecontaining fill 45 is recessed to is typically selected to dictate thedepth of the lower surface of the power rail 10.

FIG. 13 depicts one embodiment of forming a second conformal etch stoplayer 40 b, i.e., second conformal dielectric layer 40 b, on therecessed surface of the first nitride containing fill 45 that isdepicted in FIG. 12 . The second conformal etch stop layer 40 b may bedeposited on the sidewalls of the gate cut trench 5 that are above therecessed surface of the first nitride containing fill 45. The secondconformal etch stop layer 40 b is similar to the first conformal etchstop layer 40 a that has been described above with reference to FIG. 9 .Therefore, the above description of the first conformal etch stop layer40 a is suitable for describing one embodiment of forming the secondconformal etch stop layer 40 b. For example, the second conformal etchstop layer 40 b may be composed of hafnium oxide that is formed usingchemical vapor deposition.

FIG. 14 depicts one embodiment of forming a second fill material 55,e.g., second nitride containing fill material 55, atop the secondconformal etch stop layer 40 bthat is depicted in FIG. 13 . The secondnitride containing fill material 55 may be deposited to fill the spaceabove the recessed surface of the first nitride containing fill 45. Thesecond nitride containing fill material 55 is similar to the firstnitride containing fill material 45 that has been described above withreference to FIG. 10 . Therefore, the above description of the firstnitride containing fill material 45 is suitable for describing oneembodiment of forming the second nitride containing fill material 55.For example, the second nitride containing fill material 55 may becomposed of silicon nitride that is formed using chemical vapordeposition.

FIG. 15 depicts planarizing the structure depicted in FIG. 14 so thatthe upper surface of the second nitride containing fill material 55 iscoplanar with the upper surface of the interlevel dielectric 31 and theupper surface of the sacrificial gate hard mask 28′ that is not etchedto provide the gate cut trench. The planarization process may beprovided by chemical mechanical planarization.

FIG. 15 is a side cross-sectional view having the orientation alongsection line X-X (as illustrated in FIG. 1 ) depicting the finalstructure of the active gate and cut gate prior to middle of line (MOL)contact patterning and etching of the power rail interconnect. The cutgate in this second embodiment is similar to FIG. 11 but contains theadditional etch stop layer as described in FIGS. 12-14 .

This second embodiment contains similar processing steps as describedabove the above sections, including dummy gate silicon removal,replacement metal gate formation and self-aligned cap formation. The CBpower rail is also processed in the same details as described in theabove sections to form the local interconnect within the gate cuttrench.

In some embodiments, the recess depth in FIG. 15 would be where the CBpower rail resides, but across PC there would be a continuous CB powerrail line not obstructed by the etch stop layer on the cut PC sidewalls(this is etched during the SiO₂ etch and over-etch of the firstcomponent).

Having described preferred embodiments of a structure and method forforming GATE CUT WITH INTEGRATED ETCH STOP LAYER, it is noted thatmodifications and variations can be made by persons skilled in the artin light of the above teachings. It is therefore to be understood thatchanges may be made in the particular embodiments disclosed which arewithin the scope of the invention as outlined by the appended claims.Having thus described aspects of the invention, with the details andparticularity required by the patent laws, what is claimed and desiredprotected by Letters Patent is set forth in the appended claims.

What is claimed is:
 1. A method of forming a semiconductor structure,the method comprising: forming a gate structure on first and secondactive regions of the semiconductor structure; removing a portion of thegate structure to define a first gate structure on the first activeregion and a second gate structure on the second active region, whereinthe first and second gate structures are in-line with one another andspaced apart by a gate cut trench; forming a first etch stop layer inthe gate cut trench; forming a first dielectric material on the firstetch stop layer in a lower portion of the gate cut trench; forming asecond etch stop layer on an upper surface of the first dielectricmaterial; and forming a second dielectric material on the second etchstop layer in an upper portion of the gate cut trench.
 2. The method ofclaim 1, further comprising: removing a portion of the second dielectricmaterial to form a recess in the gate cut trench; and forming anelectrically conductive material in the recess.
 3. The method of claim2, wherein the electrically conductive material is selected from a groupof: tungsten, cobalt, ruthenium, titanium, aluminum, and copper.
 4. Themethod of claim 2, wherein the electrically conductive materialcomprises a portion of a power rail or power rail interconnect.
 5. Themethod of claim 2, further comprising: planarizing the electricallyconductive material to form a coplanar surface comprising an uppersurface of the electrically conductive material, an upper surface of thefirst gate structure, and an upper surface of the second gate structure.6. The method of claim 1, wherein the first etch stop layer comprises anoxide.
 7. The method of claim 6, wherein the first etch stop layercomprises hafnium oxide.
 8. The method of claim 1, wherein the secondetch stop layer comprises an oxide.
 9. The method of claim 8, whereinthe second etch stop layer comprises hafnium oxide.
 10. The method ofclaim 1, wherein the first etch stop layer and the second etch stoplayer comprise the same material.
 11. The method of claim 1, whereinforming the first etch stop layer comprises conformally depositing afirst etch stop material.
 12. The method of claim 1, wherein forming thesecond etch stop layer comprises conformally depositing a second etchstop material.
 13. The method of claim 11, wherein forming the secondetch stop layer comprises conformally depositing a second etch stopmaterial.
 14. The method of claim 13, wherein the first and second etchstop materials are the same material.
 15. The method of claim 1, whereinforming the first dielectric material on the first etch stop layer in alower portion of the gate cut trench further comprises: depositing thefirst dielectric material in the gate cut trench; and recessing thefirst dielectric material .
 16. The method of claim 1, wherein the firstand second gate structures are dummy gate structures.
 17. The method ofclaim 15, wherein the first and second gate structures are dummy gatestructures.
 18. The method of claim 1, wherein the first dielectricmaterial comprises nitride.
 19. The method of claim 1, wherein thesecond dielectric material comprises nitride.
 20. The method of claim 1,wherein the first active region comprises a first fin structure.
 21. Themethod of claim 20, wherein the second active region comprises a secondfin structure different from the first fin structure.
 22. The method ofclaim 1, wherein removing the portion of the gate structure comprises:removing upper portions of dielectric side wall spacers disposed onsidewalls of the gate structure.